Such industrial ovens are used, for example, as so-called retort ovens and serve, for example, to thermally process metals. Another field of application is in thermally processing oil shale in order to obtain oil vapour.
So that the thermal processing can be carried out in a defined atmosphere, there is provided between the rotary pipe and the supply device a sealing arrangement which comprises a gas seal. In that manner, it is also possible to adjust in the operating chamber a selective pressure (in accordance with the method, this may be excess or reduced pressure).
A necessary gap is provided between the rotating rotary pipe and the fixed material supply device and has dimensions which are as small as possible in order to prevent material from the operating chamber from reaching the gas seal via the gap.
In specific applications such as, for example, processing oil shale, the rotary pipe is operated with a material filling level of approximately 50% and more. Owing to the high filling level, the use of a rotating transfer wall or the like for introducing the material into the operating chamber is impossible.
Therefore, it has already been proposed to place a material supply chute having an upright end wall upstream of the rotating rotary pipe. Owing to the high filling level and the resultant high hydrostatic pressure in the material mound of the operating chamber, a substantial quantity of material is urged through the gap within a relatively short space of time in the ovens known in practice. Subsequently, the material quickly reaches the gas seal so that it is destroyed in a relatively short time.
DE2119650A therefore proposed a sealing arrangement which comprises a fixed cylinder which is connected to a material supply device and a cylinder which rotates with a rotary pipe, there being formed between the two cylinders an annular space, in which a helical screw component which rotates with the rotary pipe is arranged in order to convey any powder-like material which has been introduced into the annular space back into the rotary pipe. However, the material located in the rotary pipe impedes this operation so that adequate sealing is ensured in the rotary pipe only at relatively low filling levels. At relatively high filling levels of, for example, more than 50%, the material is urged out of the rotary pipe into the annular space in a substantially increased manner.